1. Field of the Invention
The present invention relates to an in-vehicle engine start control apparatus that controls an engine to automatically stop and restart appropriately by avoiding a wasteful idle operation to improve fuel efficiency of an in-vehicle engine and suppress exhaust pollution.
2. Background Art
There is disclosed a wide variety of information related to an engine automatic stop and restart control apparatus configured to automatically stop an engine when a vehicle stops because an accelerator pedal returns to the original position and a brake pedal is depressed and to restart the engine because the brake pedal is released or the accelerator pedal is depressed. For example, a fuel consumption saving type automobile disclosed in Patent Document 1 adopts a start control apparatus that controls an engine to undergo inertial rotation by stopping fuel injection and releasing an exhaust valve when the engine is suspended. When an engine rotation speed is at least not 0, the start control apparatus runs a starter motor for a speed regulation operation and connects the starter motor to the engine after rotation speed thereof is synchronized with the engine rotation speed. The apparatus in the related art described in Patent Document 1 is configured to maintain inertial rotation of the engine to the extent possible during an automatic stop and to start a speed regulation operation of the starter motor after a restart request is issued to the engine that is gradually decelerating, so that a pinion gear on the side of the starter motor is synchronously meshed with a ring gear on the side of the engine.
An engine automatic stop and restart system disclosed in Patent Document 2 adopts a start control apparatus by which a pinion gear is rotationally driven by a starter in a case where a restart request is issued during an engine rotation decreasing period, that is, since the issuance of an automatic stop request until the engine rotation stops, and adjusts at least one of pushing timing and a pushing speed of the pinion gear by predicting a time when rotations of the pinion gear and the ring gear are synchronized with each other, so that cranking by the starter is started after the both gears are synchronously meshed with each other. The apparatus in the related art described in Patent Document 2 is configured to stop the engine as soon as possible during an automatic stop and enables the decelerating engine to restart in case of early issuance of a restart request under the assumption that a restart request may be issued while the engine is in a stopped state.
A starting apparatus for vehicle disclosed in Patent Document 3 adopts a start control apparatus that maintains a coupling between a pinion gear and a ring gear independently of the issuance of a restart request while an engine is in a stopped state according to an automatic stop request and restarts the engine by rotationally driving a starter as soon as a restart request is issued. The apparatus in the related art described in Patent Document 3, however, is silent about a case where the decelerating engine is restarted according to a restart request issued immediately after an automatic stop request.
For an in-vehicle engine starting apparatus, there is a technique to apply duty control to an electromagnetic shift coil, which drives a pinion gear to be pushed toward a ring gear, using a transistor. For example, according to a starter control method disclosed in Patent Document 4, an energization current is reduced after a predetermined time from a start of energization to an electromagnetic shift coil and before a time when a pinion gear and a ring gear are predicted to come into contact with each other. Accordingly, the pinion gear is allowed to come into contact with the ring gear smoothly while the energization current is adjusted appropriately in response to a power supply voltage during the predetermined time.
Regarding fuel injection control to start an engine quickly in an in-vehicle engine starting apparatus, there is an in-vehicle engine control apparatus disclosed, for example, in Patent Document 5. Herein, a discrimination portion that discriminates a cylinder sequence for fuel injection to a multi-cylinder engine is disclosed and a description is given to a concept of asynchronous fuel injection performed before the cylinder discrimination is completed and synchronous fuel injection performed after the cylinder discrimination is completed.    Patent Document 1: JP-A-2002-070699 (Paragraphs [0008], [0009], and [0024] in Specification, FIG. 3, and Abstract)    Patent Document 2: JP-A-2005-330813 (FIG. 1 and Abstract)    Patent Document 3: JP-A-2002-221133 (FIG. 1 and Abstract)    Patent Document 4: JP-A-2002-122059 (FIG. 2 and Abstract)    Patent Document 5: JP-A-2009-030543 (FIG. 2 and Abstract)
The start control apparatus of Patent Document 1 requires release control on the exhaust valve to let the engine undergo inertial operation. Hence, this start control apparatus has problems that the control mechanism becomes complex and expensive and that an auxiliary battery and a transistor having a large current capacity are required for the speed regulation operation by the starter motor. The start control apparatus of Patent Document 2 rotationally drives the starter motor preliminarily after an engine restart request is issued. Hence, it is difficult for the pinion gear and the ring gear to be synchronously meshed with each other while the engine is decelerating. Given these circumstances, the pinion gear is forcedly pushed in an asynchronous state or in many cases the engine is restarted after the engine stops completely. This start control apparatus therefore has problems that an unusual noise occurs, the pinion gear wears, and a delayed restart makes the driver feel unnatural.
The start control apparatus of Patent Document 3 does not restart the engine while the engine is decelerating. Hence, even in a case where the engine has to be restarted immediately after an automatic stop, it becomes necessary to wait until the engine stops completely. A delay thus occurred makes the driver feel unnatural. The engine decelerates quickly when fuel injection is stopped. However, an unstable rotation state including a reverse rotation operation occurs immediately before the engine stops completely. A time required for the engine to stop completely is by no means negligibly short for the driver wishing to start the vehicle quickly.
According to the pinion gear pushing control described in Patent Document 4, a time since the pinion pushing control is started until the pinion gear comes into contact with the ring gear varies with magnitude of the power supply voltage. This poses a problem that it is difficult to control the synchronous meshing. Also, the asynchronous fuel injection described in Patent Document 5 allows the engine decelerating by inertia to restart by itself without depending on a starting electric motor. Hence, the engine operates at an inappropriate air-fuel ratio, even temporarily, and there arises a problem that such an operation causes air pollution.
The apparatus described in Patent Document 5 temporarily suspends all the controls including the fuel injection and the cylinder sequence discrimination for initialization of a microprocessor in association with the occurrence of an abnormality during operation. Hence, in order to avoid the engine from decelerating to a low rotation region in which fuel injection timing is delayed due to a time required for cylinder sequence discrimination and the engine becomes unable to start by itself, asynchronous fuel injection is performed before the cylinder sequence discrimination is completed. In this manner, when the fuel injection is stopped, it is general to also stop the accompanying control on the cylinder sequence discrimination. It is therefore necessary to perform the cylinder sequence discrimination first when the fuel injection is resumed.